OpenClinica User Manual/DisableReasonForChange
Disable Forced Reason For Change in Administrative Editing 
Users editing a completed CRF have to provide a Reason for Change for every modification. This includes newly inserted group fields and may result in a lot of unwanted Reason for Change if the CRF has been marked complete accidentally.
Workaround 1 (Disable Forced Reason for Change) 
It is possible to disable the Forced Reason for Change in the Study Parameter Configuration section if the Forced Reason For Change in Administrative Editing? is set to No.
This effects the whole study and disables the Forced Reason for Change for all CRFs.
Workaround 2 (Reset CRF status to data entry started) 
This workaround uses OpenClinica in a way it that might not be intended. Before applying this workaround to a productive environment this should be tested on a non-productive system first.
Removing and restoring the CRF resets it's status to "data entry started". Removing and restoring the whole event resets the status of all CRFs to "data entry started".